The central objective of this research is to use the structure of the gp120/CD4 complex and structure-based mimetics to design antagonists of the interaction of human cells with HIV-1, the human immunodeficiency virus responsible for AIDS. T-cell docking and entry by HIV-1, a major route of cell infiltration and resultant infecting in AIDS, is driven by specific recognition of the T-cell surface protein CD4 with the HIV envelope protein gp120. The crystallographic structure of CD4 is known, and that of its complex with gp120 is close at hand. Structural components in both protein partners have been identified which are proposed to play key roles in CD4-gp120 recognition. The advancing high resolution structural understanding of the protein participants in virus-cell recognition together with the advancing technology of mimetics design now make it possible to combine structure determination, modeling, miniprotein engineering and organic synthesis to design new antagonists for AIDS. Other components of this research program aim to utilize the high resolution X-ray crystal structure of the CD4/gp120 complex in concert with previous crystallographic and mutational analyses (a) to identify the binding sites in the CD4-gp120 interface by computational modeling and (b) transplant CD4 and gp120 binding site components such as form loops and helices into conformationally constrained miniprotein constructions to obtain miniprotein mimetics and use these to define the minimum structure that contains a sufficient number of binding sites from the parent protein that maintains a comparable interaction. The specific aims of this proposal are to (1) utilize key structural elements as determined from modeling of the high resolution structure, and subsequently miniprotein mimetics to design small molecule CD4 and/or gp120 antagonist; (2) identify novel inhibitors of gp120/CD4 to augment the rational design efforts of Specific Aim 1, by screening the SB compound bank and by synthesizing constrained peptide and semipeptide helix, gamma-turn and beta- turn mimetic libraries. Overall, this project will yield miniprotein and organic synthetic technologies for protein mimetics construction. GRANTP01GM565509001 The interaction of HIV-1 with its primary receptor, CD4, is critical for viral entry into the target cell. The conserved nature of the CD4 binding site on the HIV-1 gp120 envelope glycoprotein makes this interaction an attractive target for intervention. The goal of this Program is to identify clinically useful compounds that can inhibit the gp120-CD4 interaction, taking advantage of very recent advances in understanding the molecular details of gp120-CD4 binding. Numerous candidate antiviralmolecules directed against the gp120 CD4 interaction will be generated by all three projects in this Program. The goal of this Scientific Core is to understand the interaction of these CAMs with humanimmunodeficiency virus (HIV-1) and its components or with host cellmolecules (CD4 and chemokine receptors) important for HIV-1 entry. The specific aim of this Scientific Core are: 1) To establish high-throughput screen assays to identify inhibitors of gp120-CD4 binding; 2) To establish secondary binding and specificity assays to define molecules that are selective inhibitors of gp120-CD4 binding and to identify the molecular targets compounds; 3) To evaluate the ability of candidate antiviral molecules to inhibit HIV-1 entry and cell-cell fusion; and 4) To elevate the ability of HIV-1 to become resistant to selected antiviral molecules.